This invention relates to a jig for high temperature heat treatment, and particularly to a jig which is used for sintering various ceramics. More particularly, the invention relates to a high temperature heat-treating jig which has excellent high-temperature strength, to which ceramic material hardly adheres, and in which discoloration and color shading hardly occur.
Heretofore, as a high temperature heat-treating jig, a plate material of molybdenum or molybdenum alloy, which is a heat-resistant material, has been generally used. This plate material has been generally produced as follows. First, an ingot prepared by sintering molybdenum powder is subjected to hot working, such as forging or rolling at high temperature into a plate material. This plate material is put to practical use as a jig in its final rolled form, or it is subjected to annealing to remove distortion caused during processing distortion at a secondary recrystallization temperature or below, generally at a temperature range of 800.degree. to 1200.degree. C., and then to fabrication before being put to practical use.
However, the inventors of the present invention found that the aforesaid conventional high temperature heat-treating molybdenum jig sometimes causes discoloration and color shading of the sintered part and the molybdenum jig during sintering of ceramics (for example, at sintering temperatures of 1500.degree. to 2000.degree. C.), and sometimes causes the sintered part to adhere to the jig.